Going back to Rodalind's comment about 'untrained mum being allowed in classroom'  ;  when the local college heard that I gave private English lessons to youngsters (most stages but particularly building up to the baccalaureat),  someone from the school approached me to see if I would be interested in helping out on a once a week basis for each class, particularly for conversaton but also to give some  extra support in between their normal teaching hours. 
I almost said  'Yes'  because it interested me;  but I was told that I would not be allowed to say one word in French during all the time of the lesson, I then declined the offer because I knew I could not do a good job.  It is just the opposite to my way of teaching
I cannot see how you can explain to a student where he has gone wrong in an exercise and why, if you speak to him in a language that he barely understands in the first place !    A comparison approach with one's own mother tongue is necessary in the early stages at least. I am all for conversation lessons using the foreign language only,  but  not when it comes to explaining grammar rules etc.
If there is one subject on which by heart must be applied, it certainly is with your Irregular Verbs -  they are numerous and most of them are very common verbs, used in almost every sentence;  only a parrot fashion learning will help memorise those for little rule can explain why  the  ED ending in past tense does not always apply
 
ie
Speak,  spoke,  spoken  but  talk, talked, talked 
Anyway, all this to say they were willing to allow an non professional person,  not even a Mum, into the college.